JERUSALEM — Israeli Prime ­Minister Benjamin Netanyahu is known for being a political survivor, but the revelation this past week that a former top aide will testify against him has led to speculation that his indictment in relation to allegations of corruption is increasingly inevitable.

Ari Harow, who served as Netanyahu’s chief of staff, will turn state’s witness in two probes into the premier, Israeli police said Friday. Netanyahu has repeatedly denied any wrongdoing.

The details of the investigations — from the Cuban cigars and other lavish gifts Netanyahu is alleged to have received from prominent business executives to allegations of collusion with Israel’s dominant newspaper for favorable news coverage — have gripped Israel in recent months. Harow’s agreement to testify, though, significantly ramps up pressure on the premier, now serving his fourth term.

The agreement “has one virtually irreversible implication: an indictment against Netanyahu is coming,” an analysis in Israel’s daily Haaretz said Saturday, as the Israeli press mulled whether it could mark the end for his premiership.

On Wednesday, his wife, Sara, was questioned by police in relation to the misuse of funds allocated to the prime minister’s residence. The next day the prime minister was named as a suspect in the investigations into bribery, fraud and breach of trust in the two cases.

Meanwhile, his eldest son caused a furor as he lashed out at a website that criticized his lavish lifestyle with a Facebook post signed off with emoji of a raised middle finger and a pile of excrement.

Harow served as Netanyahu's bureau chief for two years beginning in 2008, returning in 2014 as his chief of staff. According to Israeli media reports, it was Harow who recorded conversations between Netanyahu and ­Arnon Mozes, the publisher of the daily Yedioth Ahronoth, negotiating coverage.

In exchange for giving evidence, the U.S.-born Harow will avoid jail time in a separate case of fraud and breach of trust. Instead he will do community service and pay a fine of 700,000 shekels ($190,000), according to the police statement.

While his evidence is likely to strengthen the cases against the prime minister, just how damning Harow’s testimony will be is unclear. A gag order has been imposed on the information Harow provided under interrogation.

Netanyahu’s office has dismissed the allegations against him as politically motivated.

“We completely reject the unfounded claims made against the prime minister,” it said in a statement. “The campaign to change the government is underway, but it is destined to fail, for a simple reason: there won’t be anything because there was nothing.”

Although he may be facing the most serious crisis of his tenure, Netanyahu, who has held the office for more than a decade in total, has so far managed to outlast every prime minister other than David Ben-Gurion. But there have been mounting calls from Israeli politicians for him to step down if he is charged.

Mickey Rosenthal, a Knesset member with the Zionist Union, told an Israeli radio station on Friday that the prime minister should declare himself “temporarily incapacitated” while the investigation against him is conducted.

One poll showed that three-quarters of Israelis believed that Netanyahu had “surrendered” over the decision to remove metal detectors from the entrance to the mosque site, which is holy to both Muslims and Jews, to whom it is known as the Temple Mount.

In what has been perceived as an attempt to rebuild his popularity among right-wing voters, Netanyahu announced his support Wednesday for the “Greater Jerusalem” bill, which would effectively annex several West Bank settlements. The next day he participated in a ceremony to lay the foundation stones for 1,000 new units at one of the settlements, which are considered illegal by most of the international community.

But no amount of political maneuvering is likely to distract from the mounting accusations of impropriety by the premier and his inner circle. A third corruption investigation is looking into allegations of bribery among his close associates related to a $2 billion submarine deal with Germany.